Method of preventing abrasion of plastic sheeting



Patented Sept. 8, 1942 METHOD OF PREVENTING ABRASION O PLASTIC SHEETING Edwin H. Hilborn, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing.

Application October 19, 1940,

Serial No. 361,974

6 Claims. (CI. 18-48) This application relates to a method of temporarily protecting surfaces from abrasion, and more particularly topreventing abrasion of the surfaces of'thin sheeting such as cellulose derivative sheeting and thelike.

Heretofore, in order to prevent sheeting such as cellulose derivative sheeting from abrasion while being square cut or fabricated, it is customary to interleave the sheets with tissue paper. While this is a satisfactory method of preventing such abrasion it introduces undesirable expense due to the cost of the paper which must be discarded when the cellulose derivative sheets are fabricated. In place of paper interleaves, various slip coatings have been used to prevent abrasion of uninterleaved sheets. If soft, these coatings smear readily; if hard,. they tend to scratch and otherwise abrade as readily as does an uncoated sheet. Also, in some cases the abrasion preventing coating, while needed for the use intended, is not desired on the cellulosic sheet after it has been cut. Thus the common methods of the priorart employed to prevent abrasion of cellulosic sheeting have in one way or the other several undesirable features.

An object of the invention is a method of preventing abrasion of thin sheeting.

Another object of the invention is a method f temporarily preventing surface abrasion of thin sheeting without permanently coating the surface. c

I have discovered a novel method of preventing abrasion of cellulose derivative sheets or other plastic sheets which eliminates the handlingand expense of the tissue interleavings or the pres- ,ence of a more or less permanent coating on these sheets.

In accordance with my invention I coat a long continuous strip of the cellulosic'sheet or the like with a protective surface of a material which will sublime when exposed to the air for a period of time. This material may be applied from a solution containing inactive solvents which do not attack the article being coated, and may be dried at relatively low temperatures. The long strip of sheeting is wound up into a relatively compact roll before the coating can sublime appreciably. When sections of this sheet are stacked on each other as when they are square cut, the protective coating on the surface of the sheets prevents contact between the surfaces of the acflacent sheets. Subsequent to this operation the protective coating'sublimes leaving an uncoated sheet which has not been. marred by the fabrication processes. I

The invention will be more clearly understood from the following examples of coating a cellulose acetate sheet with a temporary protective coating which will sublime on continued exposure I to air.

Example I Cellulose acetate sheeting is immersed in a A% solution of benzoic acid in toluene. The benzoic acid precipitates on the sheet to form a slip coating similar to that which would be obtained by dusting with starch. The sheet is then dried for five minutes at F. and wound into a compact roll. In the roll substantially to cut the sheets to size or otherwise handle them when they are in contact with each other,

this coating of precipitated benzoic acid pre-.

vents abrasion of the surfaces of the cellulose acetate sheets. On subsequent exposure to air, the benzoic acid disappears entirely in a matter of a few hours.

Example II Cellulose acetate butyrate sheeting is immersed in' a /g% S01llti0n of naphthalene in xylene. The naphthalenecoats out on the sheet to form a thin slip coating. The sheet is then dried for a few minutes at 100 F. The acetate.

butyrate'sheeting is then wound into a rather compact roll and substantial sublimation of the naphthalene is therefore prevented. When the sheet isunrolled, stacked and cut up into regular sized pieces, or otherwise handled, the thin naphthalene'coating will prevent abrasion of the adjacent sheets. Subsequently the naphthalene will sublime leaving a clear uncoated and unscratched sheet. I

I Example III Cellulose acetate sheeting -is immersed in a solution of 3% camphor in alcohol. The camphor will precipitate on the sheet to form a slip coating which does not attack the sheet. The coated sheeting is then dried for a few minutes at 100 F. and wound into a compact roll and substantial sublimation is prevented. When the sheet is unrolled, stacked and cut up into regular sized pieces or otherwise handled the coating of camphor will prevent abrasion of adjacent sheets. The camphor coating will then sublime leaving an unmarred sheet.

Example I V Cellulose acetate sheeting is immersed in a solution of 3% camphene in alcohol.. The cam? When it is desired into regular sized pieces or otherwise handled the coating of camphene will prevent abrasions of adjacent sheets. The camphene coating will then sublime leaving an unmarred sheet.

Example V Cellulose acetate butyrate sheeting is immersed in a solution of pi-dichlor benzene in alcohol. The p-dichlor benzenecoats out on the sheet to form a thin slip coating. The sheet is then dried for a few minutes at 100 F. The acetate butyrate sheeting is then wound into a rather compact roll-and substantial sublimation of the p-dichlor benzene is therefore prevented. When the sheet is unrolled, stacked and cut up into regular sized pieces, or otherwise handled, the thin p-dichlor benzene 'coating will prevent abrasion of the adjacent sheets. Subsequently the p-dichlor benzene will sublime leaving a clear uncoated and unscratched sheet.

It will be understood that other cellulose ester derivative sheets such as cellulose propionate, cellulose butyrate and the like as well as cellulose ether sheets such as benzyl cellulose, methyl or ethyl cellulose sheets may be protected by my novel process.

Cellulose ester sheeting which is to be coated in accordance with my present invention can be made in accordance with U. S. Patents 2,177,659; 2,177,660; 2,177,661; 2,177,658; 2,151,476 or other suitable processes known to the art.

The invention is, of course, not limited to cellulosic sheeting but may be employed with thermoplastic resin sheeting the resin bases of which may be those broadly identified as polyvinyl acetal resins, polyvinyl acetaldehyde acetal resins, or mixed polyvinyl acetal resins.

The preparation of such resins and sheetin made therefrom is disclosed in U. 8. Patents 2,197,420 and 2,197,421 of April 16, 1940.

These resin sheets may be coated with a protective coating of benzoic acid in toluene as described in Example I and this coating will satisfactorily, protect,,.them from abrasion during handling and fabrithtion. The protective coating will then sublime leaving the resin sheets without disfigurement.

While specifically applicable to sheeting, my

invention =may be extended to include application to" any surfaces which it is desirable to "protect from abrasion temporarily. Care should be before sublimation of taken that the solvent for the subliming agent is one which is a non-solvent or a relatively non-solvent of the sheet being coated.

I claim:

1. The method of temporarily preventing abrasion 'of a plastic sheet which comprises coating the sheet with a protective coating which will sublime if exposed in air for a substantial period and suppressing sublimation of the coating while forces tending to abrade the sheet are active.

2. The method of temporarily preventing abra-' sion of a plastic sheet which comprises coating the sheet with a protective coating which will sublime if exposed in air for a substantial period and suppressing sublimation of the coating by covering the coating with'another sheet also coated with a similar protecting coating while forces tending to abrade the sheet are active.

3. The method of temporarily preventing abrasion of a cellulose organic acid ester sheet which comprises coating the sheet with a protective coating which will sublime if exposed in air. for a substantial period and suppressing sublimation of the coating by covering the coating with another sheet also coated with a similar Protecting coating while forces tending to abrade the sheet are active.

4. The method of temporarily preventing abrasion of a cellulose acetate sheet which comprises coating the sheet with a protective coating which will sublime if exposed in air for a substantial period and suppressing sublimation of the coating by covering the coating with another sheet also coated with a similar protecting coating while forces tending to abrade the sheet are active.

5. The method of temporarily preventing abrasion of a polyvinyl acetal sheet which comprises coating the sheet with a protective coating which will sublime if exposed in air for a substantial period and suppressing sublimation of the coating by covering the coating with another sheet also coated with a similar protecting coating while forces tending to abrade the sheet are active.

- 6. The method of temporarily preventing abra- I sion of continuous strips of plastic sheeting during cutting andstacking operations which comprises coating the continuous sheeting with a protective coating of benzoic acid which will sublime if exposed in air for a substantial period, rolling the sheeting into a compact roll before the coating substantially sublimes and subsequently unrolling and cutting the continuous sheeting and stacking the individual cut sheets the coating occurs.

EDWIN H. HILBORN. 

